qdbm
Class Villa

java.lang.Object
  qdbm.Villa

All Implemented Interfaces:

ADBM

public class Villa
extends java.lang.Object
implements ADBM

The Java API of Villa, the advanced API of QDBM. This class depends on the native library `jqdbm'.

Field Summary

static int	CMPDEC comparing mode: compare as decimal strings
static int	CMPLEX comparing mode: compare by lexical order
static int	CMPNUM comparing mode: compare as long integers
static int	CMPOBJ comparing mode: compare as comparable objects
static int	CPAFTER insertion mode: insert after the current record
static int	CPBEFORE insertion mode: insert before the current record
static int	CPCURRENT insertion mode: overwrite the current record
static int	DCAT write mode: concatenate values
static int	DDUP write mode: allow duplication of records
static int	DDUPR write mode: allow duplication with reverse order
static int	DKEEP write mode: keep the existing value
static int	DOVER write mode: overwrite the existing value
static int	EALLOC error code: memory allocation error
static int	EBROKEN error code: broken database file
static int	ECLOSE error code: close error
static int	EFATAL error code: with fatal error
static int	EKEEP error code: existing record
static int	ELOCK error code: lock error
static int	EMAP error code: memory mapping error
static int	EMISC error code: miscellaneous error
static int	EMKDIR error code: mkdir error
static int	EMODE error code: invalid mode
static int	ENOERR error code: no error
static int	ENOITEM error code: no item found
static int	EOPEN error code: open error
static int	EREAD error code: read error
static int	ERMDIR error code: rmdir error
static int	ESEEK error code: seek error
static int	ESTAT error code: stat error
static int	ESYNC error code: sync error
static int	ETRUNC error code: trunc error
static int	EUNLINK error code: unlink error
static int	EWRITE error code: write error
static int	JBACKWARD jump mode: jump mode: step backward
static int	JFORWARD jump mode: jump mode: step forward
static int	OCREAT open mode: writer creating
static int	OLCKNB open mode: lock without blocking
static int	ONOLCK open mode: open without locking
static int	OREADER open mode: open as a reader
static int	OTRUNC open mode: writer truncating
static int	OWRITER open mode: open as a writer
static int	OXCOMP open mode: compress leaves with BZIP2
static int	OYCOMP open mode: compress leaves with LZO
static int	OZCOMP open mode: compress leaves with ZLIB
boolean	silent Whether to repress frequent exceptions.

Constructor Summary

Villa(java.lang.String name)
Get the database handle as a reader.

Villa(java.lang.String name, int omode, int cmode)
Get the database handle.

Method Summary

void	close() Close the database handle.
boolean	curfirst() Move the cursor to the first record.
boolean	curjump(byte[] key) Move the cursor to a position around a record for stepping forward.
boolean	curjump(byte[] key, int jmode) Move the cursor to a position around a record.
boolean	curjumpobj(java.lang.Object key, int jmode) Move the cursor to a position around a record composed of serializable objects.
byte[]	curkey() Get the key of the record where the cursor is.
java.lang.Object	curkeyobj() Get the key of the record composed of serializable objects, where the cursor is.
boolean	curlast() Move the cursor to the last record.
boolean	curnext() Move the cursor to the next record.
boolean	curout() Delete the record where the cursor is.
boolean	curprev() Move the cursor to the next record.
boolean	curput(byte[] val) Insert a record as the successor of the cursor.
boolean	curput(byte[] val, int cpmode) Insert a record around the cursor.
boolean	curputobj(java.lang.Object val, int cpmode) Insert a record around the cursor.
byte[]	curval() Get the value of the record where the cursor is.
java.lang.Object	curvalobj() Get the value of the record where the cursor is.
void	delete(byte[] key) Delete a record.
static java.lang.String	errmsg(int ecode) Get an error message.
boolean	error() Check whether a fatal error occured or not.
boolean	fatalerror() Check whether the database has a fatal error or not.
byte[]	fetch(byte[] key) Fetch a record.
protected void	finalize() Release the resources.
byte[]	firstkey() Get the first key.
int	fsiz() Get the size of the database file.
byte[]	get(byte[] key) Retrieve a record.
int	getindex() Get the index of the native table for database handles.
java.lang.Object	getobj(java.lang.Object key) Retrieve a record composed of serializable objects.
int	inode() Get the inode number of the database.
int	lnum() Get the number of the leaf nodes of B+ tree.
long	mtime() Get the last modified time of the database.
VillaCursor	mulcuropen() Get a multiple cursor.
java.lang.String	name() Get the name of the database.
byte[]	nextkey() Get the next key.
int	nnum() Get the number of the non-leaf nodes of B+ tree.
void	optimize() Optimize the database.
boolean	out(byte[] key) Delete a record.
boolean	outobj(java.lang.Object key) Delete a record composed of serializable objects.
boolean	put(byte[] key, byte[] val) Store a record with overwrite.
boolean	put(byte[] key, byte[] val, int dmode) Store a record.
boolean	putobj(java.lang.Object key, java.lang.Object val, int dmode) Store a record composed of serializable objects.
static void	remove(java.lang.String name) Remove a database file.
int	rnum() Get the number of the records stored in a database.
void	settuning(int lrecmax, int nidxmax, int lcnum, int ncnum) Set the tuning parameters for performance.
void	store(byte[] key, byte[] val, boolean replace) Store a record.
void	sync() Synchronize updating contents with the file and the device.
void	tranabort() Abort the transaction.
void	tranbegin() Begin the transaction.
void	trancommit() Commit the transaction.
static java.lang.String	version() Get the version information.
int	vnum(byte[] key) Get the number of records corresponding a key.
int	vnumobj(java.lang.Object key) Get the number of records corresponding a key, composed of serializable objects.
int	vsiz(byte[] key) Get the size of the value of a record.
int	vsizobj(java.lang.Object key) Get the size of the value of a record, composed of serializable objects.
boolean	writable() Check whether the database handle is a writer or not.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CMPDEC

public static final int CMPDEC

comparing mode: compare as decimal strings

See Also:

Constant Field Values

CMPLEX

public static final int CMPLEX

comparing mode: compare by lexical order

See Also:

Constant Field Values

CMPNUM

public static final int CMPNUM

comparing mode: compare as long integers

See Also:

Constant Field Values

CMPOBJ

public static final int CMPOBJ

comparing mode: compare as comparable objects

See Also:

Constant Field Values

CPAFTER

public static final int CPAFTER

insertion mode: insert after the current record

See Also:

Constant Field Values

CPBEFORE

public static final int CPBEFORE

insertion mode: insert before the current record

See Also:

Constant Field Values

CPCURRENT

public static final int CPCURRENT

insertion mode: overwrite the current record

See Also:

Constant Field Values

DCAT

public static final int DCAT

write mode: concatenate values

See Also:

Constant Field Values

DDUP

public static final int DDUP

write mode: allow duplication of records

See Also:

Constant Field Values

DDUPR

public static final int DDUPR

write mode: allow duplication with reverse order

See Also:

Constant Field Values

DKEEP

public static final int DKEEP

write mode: keep the existing value

See Also:

Constant Field Values

DOVER

public static final int DOVER

write mode: overwrite the existing value

See Also:

Constant Field Values

EALLOC

public static final int EALLOC

error code: memory allocation error

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Constant Field Values

EBROKEN

public static final int EBROKEN

error code: broken database file

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Constant Field Values

ECLOSE

public static final int ECLOSE

error code: close error

See Also:

Constant Field Values

EFATAL

public static final int EFATAL

error code: with fatal error

See Also:

Constant Field Values

EKEEP

public static final int EKEEP

error code: existing record

See Also:

Constant Field Values

ELOCK

public static final int ELOCK

error code: lock error

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Constant Field Values

EMAP

public static final int EMAP

error code: memory mapping error

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Constant Field Values

EMISC

public static final int EMISC

error code: miscellaneous error

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Constant Field Values

EMKDIR

public static final int EMKDIR

error code: mkdir error

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Constant Field Values

EMODE

public static final int EMODE

error code: invalid mode

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Constant Field Values

ENOERR

public static final int ENOERR

error code: no error

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Constant Field Values

ENOITEM

public static final int ENOITEM

error code: no item found

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Constant Field Values

EOPEN

public static final int EOPEN

error code: open error

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Constant Field Values

EREAD

public static final int EREAD

error code: read error

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Constant Field Values

ERMDIR

public static final int ERMDIR

error code: rmdir error

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Constant Field Values

ESEEK

public static final int ESEEK

error code: seek error

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Constant Field Values

ESTAT

public static final int ESTAT

error code: stat error

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Constant Field Values

ESYNC

public static final int ESYNC

error code: sync error

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Constant Field Values

ETRUNC

public static final int ETRUNC

error code: trunc error

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Constant Field Values

EUNLINK

public static final int EUNLINK

error code: unlink error

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Constant Field Values

EWRITE

public static final int EWRITE

error code: write error

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Constant Field Values

JBACKWARD

public static final int JBACKWARD

jump mode: jump mode: step backward

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Constant Field Values

JFORWARD

public static final int JFORWARD

jump mode: jump mode: step forward

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Constant Field Values

OCREAT

public static final int OCREAT

open mode: writer creating

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Constant Field Values

OLCKNB

public static final int OLCKNB

open mode: lock without blocking

See Also:

Constant Field Values

ONOLCK

public static final int ONOLCK

open mode: open without locking

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Constant Field Values

OREADER

public static final int OREADER

open mode: open as a reader

See Also:

Constant Field Values

OTRUNC

public static final int OTRUNC

open mode: writer truncating

See Also:

Constant Field Values

OWRITER

public static final int OWRITER

open mode: open as a writer

See Also:

Constant Field Values

OXCOMP

public static final int OXCOMP

open mode: compress leaves with BZIP2

See Also:

Constant Field Values

OYCOMP

public static final int OYCOMP

open mode: compress leaves with LZO

See Also:

Constant Field Values

OZCOMP

public static final int OZCOMP

open mode: compress leaves with ZLIB

See Also:

Constant Field Values

silent

public boolean silent

Whether to repress frequent exceptions.

Constructor Detail

Villa

public Villa(java.lang.String name)
      throws VillaException

Get the database handle as a reader. The same as `Villa(name, Villa.OREADER, Villa.CMPLEX)'.

Throws:

VillaException

See Also:

Villa(java.lang.String, int, int)

Villa

public Villa(java.lang.String name,
             int omode,
             int cmode)
      throws VillaException

Get the database handle.

Parameters:

name - the name of a database file.

omode - the connection mode: `Villa.OWRITER' as a writer, `Villa.OREADER' as a reader. If the mode is `Villa.OWRITER', the following may be added by bitwise or: `Villa.OCREAT', which means it creates a new database if not exist, `Villa.OTRUNC', which means it creates a new database regardless if one exists, `Villa.OZCOMP', which means leaves in the database are compressed with ZLIB, `Villa.OYCOMP', which means leaves in the database are compressed with LZO, `Villa.OXCOMP', which means leaves in the database are compressed with BZIP2. Both of `Villa.OREADER' and `Villa.OWRITER' can be added to by bitwise or: `Villa.ONOLCK', which means it opens a database file without file locking, or `Villa.OLCKNB', which means locking is performed without blocking.

cmode - the comparing function: `Villa.CMPLEX' comparing keys in lexical order, `Villa.CMPNUM' comparing keys as numbers of big endian, `Villa.CMPDEC' comparing keys as decimal strings, `Villa.CMPOBJ' comparing keys as serialized objects implementing `java.util.Comparable'. The comparing function should be kept same in the life of a database.

Throws:

VillaException

Note:

While connecting as a writer, an exclusive lock is invoked to the database file. While connecting as a reader, a shared lock is invoked to the database file. The thread blocks until the lock is achieved. `Villa.OZCOMP', `Villa.OYCOMP', and `Villa.OXCOMP' are available only if QDBM was built each with ZLIB, LZO, and BZIP2 enabled. If `Villa.ONOLCK' is used, the application is responsible for exclusion control.

Method Detail

close

public void close()
           throws VillaException

Close the database handle.

Specified by:

close in interface ADBM

Throws:

VillaException - if an error occurs.

Note:

Updating a database is assured to be written when the handle is closed. If a writer opens a database but does not close it appropriately, the database will be broken. If the transaction is activated and not committed, it is aborted.

curfirst

public boolean curfirst()
                 throws VillaException

Move the cursor to the first record.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or there is no record in the database.

curjump

public boolean curjump(byte[] key)
                throws VillaException

Move the cursor to a position around a record for stepping forward. The same as `curjump(key, Villa.JFORFARD)'.

Throws:

VillaException

See Also:

curjump(byte[], int)

curjump

public boolean curjump(byte[] key,
                       int jmode)
                throws VillaException

Move the cursor to a position around a record.

Parameters:

key - a byte array of a key.

jmode - detail adjustment: `Villa.JFORWARD', which means that the cursor is set to the first record of the same key and that the cursor is set to the next substitute if completely matching record does not exist, `Villa.JBACKWARD', which means that the cursor is set to the last record of the same key and that the cursor is set to the previous substitute if completely matching record does not exist.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or there is no record corresponding the condition.

curjumpobj

public boolean curjumpobj(java.lang.Object key,
                          int jmode)
                   throws VillaException

Move the cursor to a position around a record composed of serializable objects. The same as `curjump(qdbm.Util.serialize(key), jmode)'.

Throws:

VillaException

See Also:

curjump(byte[], int)

Note:

If serialization is failed, an instance of `VillaException' is thrown.

curkey

public byte[] curkey()
              throws VillaException

Get the key of the record where the cursor is.

Returns:

a byte array of the key of the corresponding record. If the silent flag is true and no record corresponds, `null' is returned instead of exception.

Throws:

VillaException - if an error occurs or no record corresponds to the cursor.

curkeyobj

public java.lang.Object curkeyobj()
                           throws VillaException

Get the key of the record composed of serializable objects, where the cursor is. The same as `qdbm.Util.deserialize(curkey())'.

Throws:

VillaException

See Also:

curkey()

Note:

If serialization is failed, an instance of `VillaException' is thrown.

curlast

public boolean curlast()
                throws VillaException

Move the cursor to the last record.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or there is no record in the database.

curnext

public boolean curnext()
                throws VillaException

Move the cursor to the next record.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or there is no next record.

curout

public boolean curout()
               throws VillaException

Delete the record where the cursor is.

Returns:

always true. However, if the silent flag is true and no record corresponds to the cursor, false is returned instead of exception.

Throws:

VillaException - if an error occurs or no record corresponds to the cursor.

Note:

After deletion, the cursor is moved to the next record if possible.

curprev

public boolean curprev()
                throws VillaException

Move the cursor to the next record.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or there is no previous record.

curput

public boolean curput(byte[] val)
               throws VillaException

Insert a record as the successor of the cursor. The same as `curput(val, Villa.CPCURRENT)'.

Throws:

VillaException

See Also:

curput(byte[], int)

curput

public boolean curput(byte[] val,
                      int cpmode)
               throws VillaException

Insert a record around the cursor.

Parameters:

val - a byte array of a value.

cpmode - detail adjustment: `Villa.CPCURRENT', which means that the value of the current record is overwritten, `Villa.CPBEFORE', which means that a new record is inserted before the current record, `Villa.CPAFTER', which means that a new record is inserted after the current record.

Returns:

always true. However, if the silent flag is true and no record corresponds to the cursor, false is returned instead of exception.

Throws:

VillaException - if an error occurs or no record corresponds to the cursor.

Note:

After insertion, the cursor is moved to the inserted record.

curputobj

public boolean curputobj(java.lang.Object val,
                         int cpmode)
                  throws VillaException

Insert a record around the cursor. The same as `curput(qdbm.Util.serialize(val), cpmode)'.

Throws:

VillaException

See Also:

curput(byte[], int)

curval

public byte[] curval()
              throws VillaException

Get the value of the record where the cursor is.

Returns:

a byte array of the value of the corresponding record. If the silent flag is true and no record corresponds, `null' is returned instead of exception.

Throws:

VillaException - if an error occurs or no record corresponds to the cursor.

curvalobj

public java.lang.Object curvalobj()
                           throws VillaException

Get the value of the record where the cursor is. The same as `qdbm.Util.deserialize(curval())'.

Throws:

VillaException

See Also:

curval()

Note:

If serialization is failed, an instance of `VillaException' is thrown.

delete

public void delete(byte[] key)
            throws VillaException

Delete a record.

Specified by:

delete in interface ADBM

Parameters:

key - a byte array of a key.

Throws:

VillaException - if an error occurs or no record corresponds.

errmsg

public static java.lang.String errmsg(int ecode)

Get an error message.

Parameters:

ecode - an error code.

Returns:

the message string of the error code.

error

public boolean error()
              throws VillaException

Check whether a fatal error occured or not.

Specified by:

error in interface ADBM

Returns:

true if the database has a fatal error, false if not.

Throws:

VillaException - if an error occurs.

fatalerror

public boolean fatalerror()
                   throws VillaException

Check whether the database has a fatal error or not.

Returns:

true if the database has a fatal error, false if not.

Throws:

VillaException - if an error occurs.

fetch

public byte[] fetch(byte[] key)
             throws VillaException

Fetch a record.

Specified by:

fetch in interface ADBM

Parameters:

key - a byte array of a key.

Returns:

a byte array of the value of the corresponding record.

Throws:

VillaException - if an error occurs or no record corresponds.

finalize

protected void finalize()
                 throws java.lang.Throwable

Release the resources.

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

Note:

If the database handle is not closed yet, it is closed. Every database should be closed explicitly. Do not cast the duty on the gerbage collection.

firstkey

public byte[] firstkey()
                throws VillaException

Get the first key.

Specified by:

firstkey in interface ADBM

Returns:

a byte array of the key of the first record.

Throws:

VillaException - if an error occurs or no record corresponds.

fsiz

public int fsiz()
         throws VillaException

Get the size of the database file.

Returns:

the size of the database file.

Throws:

VillaException - if an error occurs.

Note:

Because of the I/O buffer, the return value may be less than the real size.

get

public byte[] get(byte[] key)
           throws VillaException

Retrieve a record.

Parameters:

key - a byte array of a key.

Returns:

a byte array of the value of the corresponding record. If the silent flag is true and no record corresponds, `null' is returned instead of exception.

Throws:

VillaException - if an error occurs, no record corresponds.

Note:

When the key of duplicated records is specified, the value of the first record of the same key is selected.

getindex

public int getindex()

Get the index of the native table for database handles.

Returns:

the index of the native table for database handles.

getobj

public java.lang.Object getobj(java.lang.Object key)
                        throws VillaException

Retrieve a record composed of serializable objects. The same as `qdbm.Util.deserialize(get(qdbm.Util.serialize(key)))'.

Throws:

VillaException

See Also:

get(byte[])

Note:

If serialization is failed, an instance of `VillaException' is thrown.

inode

public int inode()
          throws VillaException

Get the inode number of the database.

Returns:

the inode number of the database file.

Throws:

VillaException - if an error occurs.

lnum

public int lnum()
         throws VillaException

Get the number of the leaf nodes of B+ tree.

Returns:

the number of the leaf nodes.

Throws:

VillaException - if an error occurs.

mtime

public long mtime()
           throws VillaException

Get the last modified time of the database.

Returns:

the last modified time of the database.

Throws:

VillaException - if an error occurs.

mulcuropen

public VillaCursor mulcuropen()
                       throws VillaException

Get a multiple cursor.

Returns:

a multiple cursor.

Throws:

VillaException

Note:

Even if plural cursors are fetched out of a database handle, they does not share the locations with each other. Note that this method can be used only if the database handle is connected as a reader.

name

public java.lang.String name()
                      throws VillaException

Get the name of the database.

Returns:

the string of the name of the database.

Throws:

VillaException - if an error occurs.

nextkey

public byte[] nextkey()
               throws VillaException

Get the next key.

Specified by:

nextkey in interface ADBM

Returns:

a byte array of the key of the next record.

Throws:

VillaException - if an error occurs or no record corresponds.

nnum

public int nnum()
         throws VillaException

Get the number of the non-leaf nodes of B+ tree.

Returns:

the number of the non-leaf nodes.

Throws:

VillaException - if an error occurs.

optimize

public void optimize()
              throws VillaException

Optimize the database.

Throws:

VillaException - if an error occurs.

Note:

In an alternating succession of deleting and storing with overwrite or concatenate, dispensable regions accumulate. This method is useful to do away with them. This method should not be used while the transaction is activated.

out

public boolean out(byte[] key)
            throws VillaException

Delete a record.

Parameters:

key - a byte array of a key.

Returns:

always true. However, if the silent flag is true and no record corresponds, false is returned instead of exception.

Throws:

VillaException - if an error occurs or no record corresponds.

Note:

When the key of duplicated records is specified, the first record of the same key is deleted. The cursor becomes unavailable due to updating database.

outobj

public boolean outobj(java.lang.Object key)
               throws VillaException

Delete a record composed of serializable objects. The same as `out(qdbm.Util.serialize(key))'.

Throws:

VillaException

See Also:

out(byte[])

Note:

If serialization is failed, an instance of `VillaException' is thrown.

put

public boolean put(byte[] key,
                   byte[] val)
            throws VillaException

Store a record with overwrite. The same as `put(key, val, Villa.DOVER)'.

Throws:

VillaException

See Also:

put(byte[], byte[], int)

put

public boolean put(byte[] key,
                   byte[] val,
                   int dmode)
            throws VillaException

Store a record.

Parameters:

key - a byte array of a key.

val - a byte array of a value.

dmode - behavior when the key overlaps, by the following values: `Villa.DOVER', which means the specified value overwrites the existing one, `Villa.DKEEP', which means the existing value is kept, `Villa.DCAT', which means the specified value is concatenated at the end of the existing value, `Villa.DDUP', which means duplication of keys is allowed and the specified value is added as the last one, `Villa.DDUPR', which means duplication of keys is allowed and the specified value is added as the first one.

Returns:

always true. However, if the silent flag is true and replace is cancelled, false is returned instead of exception.

Throws:

VillaException - if an error occurs or replace is cancelled.

Note:

The cursor becomes unavailable due to updating database.

putobj

public boolean putobj(java.lang.Object key,
                      java.lang.Object val,
                      int dmode)
               throws VillaException

Store a record composed of serializable objects. The same as `put(qdbm.Util.serialize(key), qdbm.Util.serialize(val), dmode)'.

Throws:

VillaException

See Also:

put(byte[], byte[], int)

Note:

If serialization is failed, an instance of `VillaException' is thrown.

remove

public static void remove(java.lang.String name)
                   throws VillaException

Remove a database file.

Parameters:

name - the name of a database file.

Throws:

VillaException - if an error occurs.

rnum

public int rnum()
         throws VillaException

Get the number of the records stored in a database.

Returns:

the number of the records stored in the database.

Throws:

VillaException - if an error occurs.

settuning

public void settuning(int lrecmax,
                      int nidxmax,
                      int lcnum,
                      int ncnum)
               throws VillaException

Set the tuning parameters for performance.

Parameters:

lrecmax - the max number of records in a leaf node of B+ tree. If it is not more than 0, the default value is specified.

nidxmax - the max number of indexes in a non-leaf node of B+ tree. If it is not more than 0, the default value is specified.

lcnum - the max number of caching leaf nodes. If it is not more than 0, the default value is specified.

ncnum - the max number of caching non-leaf nodes. If it is not more than 0, the default value is specified.

Throws:

VillaException - if an error occurs.

Note:

The default setting is equivalent to `settuning(49, 192, 1024, 512)'. Because tuning parameters are not saved in a database, you should specify them every opening a database.

store

public void store(byte[] key,
                  byte[] val,
                  boolean replace)
           throws VillaException

Store a record.

Specified by:

store in interface ADBM

Parameters:

key - a byte array of a key.

val - a byte array of a value.

replace - whether the existing value is to be overwritten or not.

Throws:

VillaException - if an error occurs or replace is cancelled.

sync

public void sync()
          throws VillaException

Synchronize updating contents with the file and the device.

Throws:

VillaException - if an error occurs.

Note:

This method is useful when another process uses the connected database file. This method should not be used while the transaction is activated.

tranabort

public void tranabort()
               throws VillaException

Abort the transaction.

Throws:

VillaException - if an error occurs.

Note:

Updating a database in the transaction is discarded when it is aborted. The state of the database is rollbacked to before transaction. Any other thread except for the one which began the transaction should not call this method.

tranbegin

public void tranbegin()
               throws VillaException

Begin the transaction.

Throws:

VillaException - if an error occurs.

Note:

If a thread is already in the transaction, the other threads block until the prius is out of the transaction. Only one transaction can be activated with a database handle at the same time.

trancommit

public void trancommit()
                throws VillaException

Commit the transaction.

Throws:

VillaException - if an error occurs.

Note:

Updating a database in the transaction is fixed when it is committed successfully. Any other thread except for the one which began the transaction should not call this method.

version

public static java.lang.String version()

Get the version information.

Returns:

the string of the version information.

vnum

public int vnum(byte[] key)
         throws VillaException

Get the number of records corresponding a key.

Parameters:

key - a byte array of a key.

Returns:

the number of corresponding records. If no record corresponds, 0 is returned.

Throws:

VillaException - if an error occurs.

vnumobj

public int vnumobj(java.lang.Object key)
            throws VillaException

Get the number of records corresponding a key, composed of serializable objects. The same as `vnum(qdbm.Util.serialize(key))'.

Throws:

VillaException

See Also:

vnum(byte[])

Note:

If serialization is failed, an instance of `VillaException' is thrown.

vsiz

public int vsiz(byte[] key)
         throws VillaException

Get the size of the value of a record.

Parameters:

key - a byte array of a key.

Returns:

the size of the value of the corresponding record. If multiple records correspond, the size of the first is returned. If the silent flag is true and no record corresponds, -1 is returned instead of exception.

Throws:

VillaException - if an error occurs.

vsizobj

public int vsizobj(java.lang.Object key)
            throws VillaException

Get the size of the value of a record, composed of serializable objects. The same as `vsiz(qdbm.Util.serialize(key))'.

Throws:

VillaException

See Also:

vnum(byte[])

Note:

If serialization is failed, an instance of `VillaException' is thrown.

writable

public boolean writable()
                 throws VillaException

Check whether the database handle is a writer or not.

Returns:

true if the handle is a writer, false if not.

Throws:

VillaException - if an error occurs.